*{
	margin: 0;
	padding: 0;
}
.demo{
	width: 345px;
	height: 150px;
	margin: 0 auto;
	margin-top: 15px;
	background-color: skyblue;
	border: 1px solid black; /* no */
	#test{
		width: 100px;
		height: 100px;
		background-color: pink;
	}
}